This invention relates to microwave circuits, and particularly, to basic microwave circuits with which various microwave devices of different functions can be realized with simple structure without need of waveguide converter portions.
Recently, study on miniaturization of microwave circuits has progressed and integrated-circuit (so-called IC) technology therefor has been developed. According to such technique, microwave circuits are formed in small size by metal-evaporating circuit elements consisting of a strip line or slotted line on dielectric or magnetic base plates. However, with respect to loss these are inferior to waveguides as transmission line, so that microwave devices using IC circuits, in general, are constructed by a combination of IC circuits and waveguides as the transmission line, both of them being connected by means of waveguide converters. Therefore, as a whole of the device an extra space is required owing to the waveguide converter portion and loss caused thereat is added. If circuit elements were formed inside a waveguide, unless all of them are constructed on a one-body plate inserted into it, mechanical working therefor needs a considerably higher degree of machining and assembling, so that such a way is not suitable for mass-production and presents difficulty of reduction in size.